Artist's concept of a view across the surface of Themisto towards Jupiter and its moons.

IMAGE SPECS: Royalty Free

Description:
Artist's concept of a view across the surface of Themisto towards Jupiter and its moons. This is how Jupiter and its Galilean satellites may appear from the surface of Jupiter's tiny moon Themisto. In this image the artist is suggesting that Themisto has an ancient, dusty and heavily cratered surface with the occasional, and fanciful, outcropping of dirty water ice. At a distance of 4.7 million miles, Jupiter subtends an angle of 1.1 degrees (the moon subtends an angle of 0.5 degrees in Earth's sky). The Galilean satellites are, left to right, Ganymede, Europa, Io, and on the far right Callisto. Not much is known about Themisto. It was first discovered in 1975, then lost, then rediscovered in 2000. Themisto is the next significant body orbiting Jupiter beyond Callisto. Beyond Themisto are another 54 known jovian satellites, the furthest of which has an orbital radius of 19 million miles. With a mean diameter of only 5 miles and an albedo (surface brightness) about half that of the Moon, no earthbound telescope or interplanetary probe has yet revealed any details of Themisto's surface. This satellite is far too small to host an atmosphere, and too small even for its own gravity to pull it into a spherical shape like its relatively massive Galilean cousins. A visiting astronaut could easily propel him/herself into orbit with a single jump.